M needle and seat

[Doc 2]

Is there a source for a brass needle for the carb? I have tried the viton tip from several different brand kits and none of them hold. I have a problem with my M and a 400 that I have been working on. The 400 sat for about 42 years in a barn. I just got it going this winter. Runs good except for the carb issue. Any ideas would be helpful. Brian

 

[Janicholson]

A primary reason for a new needle (either brass, or Viton) fails to seat is the little wear dimple in the tang that pushes it upward into the seat. This can be fixed by soldering in a silver solder filling and filing flat, or flattening from the opposite side. Jim

 

[Doc 2]

A primary reason for a new needle (either brass, or Viton) fails to seat is the little wear dimple in the tang that pushes it upward into the seat. This can be fixed by soldering in a silver solder filling and filing flat, or flattening from the opposite side. Jim

I'll have to try that. Thanks

 

[rustred]

Is there a source for a brass needle for the carb? I have tried the viton tip from several different brand kits and none of them hold. I have a problem with my M and a 400 that I have been working on. The 400 sat for about 42 years in a barn. I just got it going this winter. Runs good except for the carb issue. Any ideas would be helpful. Brian

the needles are not brass and never did see a brass needle. if it was brass it would wear out in a hurry. i dont know what metal they use but i have seen many metal tips with wear ridges in them. even the rubber tip ones you can see the wear seat. is the float level set correctly to put pressure on the needle to hold it closed. i believe its 2 5/16 from carb top base to the bottom of the float when inverted. if no float scale then hold it upside down and eye it up level.

 

[Doc 2]

I'll dig into it tomorrow. I did set the float per the directions in the kit. It is a new float, but I will pay more attention to the tab on the needle maybe adjusting that a bit and resetting the float level accordingly.

 

[rustred]

I'll dig into it tomorrow. I did set the float per the directions in the kit. It is a new float, but I will pay more attention to the tab on the needle maybe adjusting that a bit and resetting the float level accordingly.

and one more thing... are u squeezing the float pin so it dont slide out and that is very well what will cause your problem. the pin will slide out and cock the float and then u get flooding. you said u have a new float so nothing to worry about a tab which there is no tab. the float is set by bending the float arms. and once the float is set its set no need to be resetting it.

 

[Doc 2]

The pin is not cocked and all is free. I will have to look at everything in there. On the 400 there is a slight drip out the weep hole in the bottom of the venturi. On my M it is worse. I'll just work with the parts I have and figure it out. Thanks all.

 

[rustred]

and one more thing, when is this leaking happening? on start up its perfectly normal to have gas leak out the weep hole at the bottom. if you come in the morning and its dripping then that is a problem .

 

[Doc 2]

On the 400 it is a little all the time gas is on at the sediment bowl. On my M it is okay before starting, runs a little rough as if flooding. Engine off it is a flood out the weep hole until gas is shut off.

 

[Janicholson]

A primary reason for a new needle (either brass, or Viton) fails to seat is the little wear dimple in the tang that pushes it upward into the seat. This can be fixed by soldering in a silver solder filling and filing flat, or flattening from the opposite side. Jim

The seat could be loos in the upper housing, leaking despite the needle. A second thought is to take the carb off and work on a bench to assess the leak. With the bowl off the carb, and it turned upside down with the float and needle in place, there should be no leakage with 4 psi of air on the input fitting. (not a bunch of pressure!!) Jim

A primary reason for a new needle (either brass, or Viton) fails to seat is the little wear dimple in the tang that pushes it upward into the seat. This can be fixed by soldering in a silver solder filling and filing flat, or flattening from the opposite side. Jim